Oil-insulated transformer



Feb. 19 1924. I 1,483,922

c. D. AINSWORTH OIL INSULATED TRANSFORMER Original Filed March 17. 1919 4 Sheets-Sheet 1 J2 47 /5 v fiveflivi.

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Feb. 19 1924. 1,483,922 C. D. AINSWORTH oxL INSULATED TRANSFORMER cri inl Fileq March 17. 1919 4 Shee ts-Sheet 2- Feb. 19 1924.

C. D. AINSWORTH OIL INSULATED TRANSFORMER Original Filed March 17. 1919 4 Sheets-Sheet 5 Ji'nveh 302" 5 Ohm D. W

Feb. 19 1924. 1,483,922

- c. 0. AINSWORTH OIL INSULATED TRANSFORMER Original Filed March 17. 1919 4 Sheets-Sheet 4 Jiwvezz 702".

Patented Feb. 19, 1924.

UNITED STATES 1,483,922 PATENT OFFICE.

CHESTER n. Amswomn, or WOLLASTON, MASSACHUSETTS, ASSIGNOR T SEARS B. coNnI'r, .73., or BROOKLINE, MASSACHUSETTS.

OIL-INSULATED raansronmna.

Application filed March 17, 1919, Serial No. 283,091. Renewed January 8, 1924.

To all whom it may concern:

Be it known that I, CHESTER D. AINswoRTI-i, a citizen of the United States, a resident of Wollaston, in the county of Norfolk and State of Massachusetts, have invented an Improvement in Oil-Insulated Transformers, of which the following a specification.

My invention relates to current trans- 1e formers adapted for use on high potential circuits.

Because of the high potential impressed upon the primary coils of current transformers of the type to which this invention it relates, the provision of proper insulation between the primary and secondary coils is a matter of great importance. The ordinary type of transformer employed on high potential circuits is formed with the usual laminated core over which the primary and sec ondary coils are disposed. Said coils are usually insulated from the core by thick layers of tape and suitable insulating ma terial, as micanite and the like, and the coils themselves impregnated with a suitable insulating material which, if the impregnating process is properly formed, permeatesthe entire mass of the coil. The impregnatingmaterial employed is fiuid at the :10 temperature at which the process is performed and, throughout the range of temperatures at which the'transformer is designed to operate is solid, or at least is (lesigned to be practically so. The primary and secondary coils of the transformer are insulated from each other by large skirts or aprons formed of sheets of insulating material which are inserted between said coils and extended upwardly therefrom a comparatively great distance to provide for a long leakage path therebetween.

The entire assembled transformer is immersed in oil and the oil may also assist in insulating the primary and secondary coils from each other. The insulating properties of the oil are but little considered, however, in the design of the proper insulation between the coils and core of the transformer as the solid. insulation is relied upon to provide for the satisfactory operation of the transformer upon the circuit for which it is designed.

The construction above described, while suitable for use on circuits of fairly low voltagessay below 25,000 volts, is not satisfactory or even desirable for voltages above this value. The process of impregnating the cores with the insulating impregnating material is long, difficult and expensive. If the process is not faithfully carried out the o0 entire mass of the core is not: permeated with the impregnating material and, as a consequence, weak spots in the coil are present or may develop, which may seriously impair the value of the impregnating material .06 as an insulator. Furthermore, there is no positive way to determine the thoroughness of the impregnating process other than a break-down test of the coil which is obviously not satisfactory. For high voltages the length of the aprons interposed between the primary and secondary coils, or the distance to which the aprons extend above and beyond said coils, must be so great, in order that an adequate leakage path be provided 76 therebetween, that the enclosing casing for the transformer must be of relatively large dimensions and thereby must occupy an undesirable amount of space.

An object of my invention is in the pro- 80 vision of a transformer so constructed and arranged that the oil in which the transformer is immersed serves as substantially the sole insulation between the primary and secondary coils whereby the necessity for 86 impregnating the coils is obviated and the expense of construction of the transformer thereby considerably reduced.

A yet further object of my invention resides in the structural features of the trans- 90 former and associated parts which are more fully set forth in the detailed description.

Fig. 1 is an elevation of an oil insulated transformer embodying my invention and with the oil receptacle partly broken. away to show the transformer construction.

Fig. 2 is a front elevation of the transformer and supporting frame therefor, removed from the receptacle.

Fig. 3 is a side elevation of Fig. 2.

Fig. 4: is a plan view along lines 1 of Fig. 1.

Fig. 5 is a front elevation of the trans-- former core with the secondary coil wound thereon.

Fig. 6 is a side elevation of Fig. 5.

Fig. 7 is an edge view of one of the primary coils.

Fig. 8 is a detail of one of the primary supporting blocks.

Fig. 9 is a plan detail of the primary coil connectors arranged for the series connection of the coil.

Fig. 10 is a plan detail of the coil connec tors arranged for the parallel connection of the coils.

Fig. 11 is a detail of a leg of a trans former.

Fig. 12 is a secondary view of the transformer lead insulator.

Fig. 13 is a plan view of Fig. 12.

The transformer embodying my invention is. or may be, enclosed in the oil receptacle or casing 10 and comprising the bottom plate 11 and top plate or cover 12 and side walls. The side walls may be arranged in recesses or grooves in said plates for fluid tight connection tluzrewith or any other suitable manner and said two plates with the side walls therebetween are clamped solidly together by the tie-rods 13. The primary lead extensions 14 and 15 of the primary coil are extended through the insulator 16 which extends through the cover 12 and is bolted thereto and said leads are secured to terminal members 17 and 18 arranged on the top of said insulator and to which connection is adapted to be made with a high tension circuit. This construction follows more or less common practice. The secondary leads 19 and 20 are extended from the transformer secondary through a. conduit 21 formed in the cover 12 for connection with suitable instruments or apparatus. The transformer is arranged to be entirely supported and suspended from the top plate or cover 12. The mechanical connection between the transformer and the top plate 12 is through the oppositely disposed lugs 23 and 24:. formed on the under side of the top plate or cover 12. Vertical s! rips 25 and 26 are bolted thereto and e.\'- tend downwardly therefrom and between which the transformer and its associated parts are connected.

The transformer core 27 is shaped into a rectangular structure and is built up of rectangular laminte assembled together in the usual manner to form a closed magnetic circuit. Strips 28 and 29 are secured to the vertical rods 25 and 26 and the ends thereof are reflexed inwardly toward each other to such an extent that the distance between the lGflGXOCl ends is substantially equal to that of the length of a side of the transformer core; and the transformer core is disposed in the recesses so formed. thereby being supported by said strips.

Tie-straps comprising the two complemental portions 30 and 30 are clamped together by means of bolts 31 around the legs of the transformer core disposed in the strips 28 and 29 and about the refiexed ends of said strips 29 to thereby bind the laminations of the transformer core securely together to form a rigid structure at the same time to unite the transformer core solidly to the supporting strips 25 and 26. The retlexed ends of said transformer core-holding strips 28 and 29 are upturned as shown at 32 to form lips which serve to retain the tie-straps from displacement therefrom. The inner edges of said tie-straps are formed with cars 33 which are bent inwardly toward each other and serve to engage the edges of the top lamina: of the transformer core and prevent their displacement.

Since the out-turned ends of said strips 28 and 29 hold the tie-straps from displacement toward the centre of the transformer and the laminations of the two legs of the transformer are abutted solidly against said straps 28 and 29 and the cars 33 of said straps are bent inwardly against the outer laminations of the core. this Sil'lltl ure serves to hold the transformer. core and the vertical straps 25 and 26 into firm and rigid engagement.

The secondary coil 35 is formed on. the top leg 36 of the transformer core before said leg is assembled into the transformer core and may be wound on an insulating sheath 37 arranged on said core, and said sheath may be relatively thin as it need have but low insulating value. A layer or two of tape as shown may be wound over the completed coil to hold the convolutions thereof from displacement.

As shown in Fig. 1 the primary coil is formed of two coils 40 which are identical in construction and arranged back to back as shown in Fig. 2, connected to form one complete and unitary primary coil. The coil 40 is wound to a relatively large in ternal diameter as compared with the external diameter of the secondary coil whereby when said coils are in assembled position, as shown in Fig. there will be a relatively large space between them which is adapted to be filled by the oil in the transformer casing; which oil is adapted to serve as substantially the sole insulating medium between said coils. Said primary coils are wound with the proper number of turns and the terminals thereof are extended upwardly. The terminals of one coil are so arranged in relation to those of the other coil that the coil connectors hereinafter to be described can unite the coils either in series or in parallel. For this purpose the inner terminals 4-1 of each coil is extended upwardly and has a contacting face substantially in the plane of the outer edge of the coil. The outer lead is extended to one side of the vertical line of the coil and the centre of its terminal is arranged to be slightly beyond the centre face of the coil as is shown in Figs. 2 and 7. \Vith such construction, when the two coils 40 are be clamped therebetween.

placed back to back to form a unitary primary coil, the coil interconnecting means may be quickly arranged to connect the coils either in parallel or in series.

Cross strips 43 and 44 are secured to said vertical rods 25 and 26 near the top and bottom ends thereof and the ends of said cross strips are reflected as shown at 45 and 46 and bars 47 of insulating material, as wood, are secured thereto by means of screws 48. Said bars serve as a part of the primary coil support. The ends ofl said bars are extended beyond the cross strips 43 and 44 and are cut off on a circular are as shown at 49 to substantially conform to the inner diameter of the enclosing casing 10, whereby the transformer supporting structure is prevented from lateral movement by said casing 10. When the transformer is permanently located in its installation this support may not be necessary as the transformer is suspended from the top plate or cover 12 and is adapted to hang vertically downward. When, however, said transformer is in shipment or is tilted away from a vertical plane such support may be necessary in order to prevent the vertical rods 25 and 26 from being bent and, when the transformer is again placed in vertical position, from thereby causing the transformer to assume a displaced position within the receptacle. The primary coil supports include the vertical bars or rods 50 and 50, 51 and 51 of rectangular form supported by bolts 52 of the top and bottom bars 47 on the opposite of the transformer su porting structure. These strips are forme of an insulating material, as of wood, and the transformer is adapted to be clamped between them. The distance between the outer surfaces of said rods 50 and 51, and 50* and 51* is substantially equal to that of the outer diameter of the primary core and the width of said strips is substantially equal to the depth of the primary core so that the entire width of the coil may The primary core is supported between said rods by the blocks '53. The inner surfaces are curved as at 54 to substantially conform to the outer circumference of the coil and the coil is adapted to be placed between said blocks as shown in Fig. 3-, which engage the circumference of the coil, to thereby hold the coil from displacement. The vertical bars 50 and 50 and 51 and 51 are secured to the supporting frame a fixed distance apart. The width of the assembled primary coil comprising the two coils 40 may be somewhat less than the distance between said vertical bars due to the different number of turns and sizes of wire of which these coils may be. formed and therefore shims of insulating material are placed between said coils as at Fig. 2 in order to bring up the width between the opposite faces of said coils to approximately that between the bars 50 and 50 and 51 and 51. Said primary coil, supporting blocks are each formed of a width equal to that of the average width of each coil 4-0 and the insulating shims 60 are extended between said blocks 53. The two complemental portions of the primary coil with interposed shims and the blocks are clamped together by means of bolts 61 which pass between said insulating shims and said blocks. Said blocks 53 are provided with elongated openings or slots 62 therein through which. said bolts are adapted to pass; and by the provision of such slots the blocks may be moved relatively to the bars 50, 50, 51, 51 to provide for slight differences in diameter of the primary coil. By the coil clamping means above described the opposite portions of the coil are securely clamped to the supports to prevent the lateral displacement of the coil and by the provision of the blocks 53, the coil is restrained from movement in the plane of its diameter, whereby the coil is held from displacement in any direction.

The primary lead terminals or extensions 1 c and 15 are extended through the centre opening in the insulator 16 and at their lower ends are formed with spaced apart parallel end portions 14 and 15 which are adapted to be secured to the outer taps or leads 41 of the two primary coils 40 to thereby provide for the connection of said coil with the line. The coil interconnecting means, by which the two halves of the coils may be connected in series or in multiple, comprises the two L shaped connectors 71 and 72, one of which is adapted to be secured to the outer lead or terminal of one coil by means of the screw 7 8, and the other of which is adapted to be secured to the outer lead or terminal of the other coil by means of the screw or bolt 74. For the series connection of the two coils the two connectors 71 and 72 are arranged as shown in Fig. 3 or in Fig. 10 with the arm of one connector beneath and in contact with the arm of the other connector and said arms secured together by a screw or bolt 7 hen it is desired to connect two coils in parallel the bolt is removed and the bolts 73 and 74 are loosened to permit the connectors to be rotated respectively to the left and right, Fig. 11 or Fig. 4c, for con nection with the right and left hand inner leads or taps of said coils. It is seen that by this simple arrangement of connectors and by the proper spacing of the end taps or coils, the change from series to parallel connection may be easily and quickly performed and without the necessity for removing the coil connectors.

It should be noted that the two arms of the membe s it and T2 are made of unequal whereby one connector may be used in either position, and the opening through which the screws 73 and 7% and 75 are adapted to pass is slotted whereby the members may be moved relatively to the taps of the coils for their proper engagement.

Claims:

1. A transformer comprising a core forming a clos d magnetic circuit, a secondar coil wound thereon, a primary coil arranged concentric with said secondary coil, the inner diameter of said primary coil adapted to be comparatively great as regards the onter diameter of the sectmdary coil whereby rid primary coil is spaced a comparatively great distance from said secondary coil. said primary coil also spaced a com atively great distance from any component of said core, insulating supports iiidependent of said core and secondary coil anged to hold said prii'nary coil in position, a receptacle adapted to contain oil in "hich said transformer is inmiersed, said oil adapted to fill the space between said coils and core and comprise the sole insulation between said primary coil and secondary coil and core a cover for said receptacle, and insulated terminals carried by said cover and connected with said priniary coil.

The combination of a casing adapted to contain oil, and a transformer immersed in the oil having a core forming a closed magnetic circuit, a secondary coil, disposed on one leg of said core and a primary coil disposed in the plane of said secondary coil and spaced relatively great distance from said core and secondary coil and the space therebetween filled with oil which constitutes the sole insulating medium between the primary coil and said secondary coil and core, and insulating means independent of said core to support said primary coil in the aforesaid relation.

3. A transformer comprising a casing formed with side walls and top and bottom plates and adapted to contain oil in which the transformer components are immersed, transformer components arranged within said casing, a support for said components including two oppositely-disposed members extended upward from said components, means securing said members to the top plate of the casing, said components and support being otherwise unsecured within s: d casing, said members adapted to be rela tively flexible and bend upon a sidewise pressure thereon, and projecting members extended from said support adapted to engage the side walls of the casing upon the flexing of said members to thereby maintain said transformer components in spaced posi tion within said casing.

4:. A transformer comprising a casing raving side walls and top and bottom plates,

transformer components arranged within said casing, and a support for said components attached to and suspended from the top plate of the casing having laterally extended portions terminating adjacent and engageable with the side walls of the casing to prevent sidewise movement of said transformer components and support within said casing.

A transformer comprising a core, a secondary coil arranged thereon, a primary coil disposed about said secondary coil and spaced therefrom, supporting means for said core, and other means to support said primary coil independently of said core and secondary coil, a receptacle adapted to contain oil in which the transformer is immersed, and a cover for said receptacle by which said transformer is supported.

6. A transformer con'iprising a core, a secondary coil thereon, supporting means for said core, a primary coil and sepa ate supporting means for said primary coil comprising opposed insulating members between which said coil is disposed and clamped.

7. A transformer comprising a core, a secondary coil arranged thereon, a supporting structure for said core including two oppositely disposed pairs of members between which said core is disposed, a primary coil disposed over said secondary coil and core and spaced therefrom and received between said members, and supporting-members arranged between said members adapted to engage the periphery of said coil and support said coil in position, and means to draw the members of each pair toward each other to clamp said coil therebetween.

8. A transformer comprising a core, a secondary coil arranged thereon, a support ing structure for said core including two oppositely-disposed pairs of members between which said core is disposed, a primary coil disposed over said secondary coil and core and spaced therefrom and received be tween said members, supporting-members arranged between said members adapted to engage the periphery of said coil and support it in position having means for their adjustment relative to said members for the reception of primary coils of sligthly varying dimensions, and means to draw said primary members toward each other to clamp said coil therebetween.

9. A transformer comprising a core, a secondary coil arranged thereon, a supporting structure for said core including two oppositely disposed pairs of members between which said core is disposed, a primary coil disposed over said secondary coil and core and spaced therefrom, having opposite portions thereof disposed between said members, bolts extended between said members by which said members and primary coil are clamped together, coil supporting-members arranged on said bolts between said members adapted to engage the periphery of said coil to support it in spaced relation about said secondary coil and core, said supportingmembers having elongated openings therein through which said bolts are extended whereby said supporting-members are adjustable for the reception of primary coils of slightly differing dimensions.

10. A transformer comprising a core, a secondary coil arranged thereon, a primary coil disposedover said core and spaced therefrom and supporting members between which opposite portions of said primary coil are adapted to be clamped, spaced a fixed distance apart, said primary coil formed of two complemental portions arranged back to back and electrically connected, the total thickness of said complemental portions adapted to be less than the distance between said supporting members, and insulating spacing means arranged between said portions to insulatingly separate them and increase the thickness of said primary coil whereby it may be clamped between said supporting-members and held in spaced relation.

11. A. transformer comprising a substantially rectangular laminated structure, a core supporting member formed with corereceiving portions adapted to snugly receive a leg of the core and hold the laminations thereof from longitudinal and endwise dis placement, and a clamping member adapted to engage the core and said core supporting member to hold said laminations from sidewise displacement.

12. A transformer comprising a substantially rectangular laminated structure, a core-supporting member adapted to snugly receive a leg of the core and hold the laminations thereof from longitudinal and endwise displacement, a clamping member adapted to engage the core and said core supporting member to hold said laminations from sidewise displacement, said core-supporting member being formed with upturned portions adapted to engage said clamping member and hold it in position thereon, said clamping member being formed with inturned lips adapted to en gage the outer laminations of said leg and clamp them thercbetween and the core-supporting member.

13. A transformer comprising a substantially rectangular laminated structure, two core-supporting members in which opposite legs of said transformers are received, and clamping members secured about said coresupporting members and said transformer legs.

14. A transformer comprising a substantially rectangular laminated structure, two core-supporting members in which opposite legs of said transformer are received, clamp ing members secured about said core-supporting members and said transformer legs, and transformer-supporting bars secured to said core-supporting members and extended thereabove.

15. A transformer having two primary coils adapted for series and parallel connection having their terminals arranged in proximity, a terminal of each coil adapted for connection to the line, and coil-connecting members pivotally connected with the other terminals arranged to be moved into connection with each other and with said first-named terminals to connect said coils in series and parallel relation.

16. A transformer having two primary coils adapted for series and parallel connection having their terminals arranged in proximity at right angles to each other, opposite similar terminals adapted for connection to the line, and L-shaped coil-conneeting members pivotally connected with said other terminals arranged to be moved into connection with each other and with said first-named terminals to connect said coils in series and parallel relation.

In testimony whereof, I have signed my name to this specification, in the presence of two subscribing witnesses.

CHESTER D. AINSVVORTH.

Witnesses:

ARTHUR C. KELLE, H. B. DAVIS. 

